Predator/Clone Carb Building

E173

New Member
#1
One area of the clone/Predator engines I just can't find info on, but want to start doing myself is taking the carburetors from stock and building them into performance carbs. Yeah, I can buy one, and I know everyone has their opinion as to who and where and even what type, but for me that takes the fun out of it. Is there a book, video, someone with an old notebook full of scribblings, something out there that can guide me though the process?

Short version, I race a stock appearing class and am pretty good with the motor, but other than changing jets, if I want something of an upgrade on the carb I've had to buy them...I don't want to do that anymore if I can help it.

No, I'm not looking to be a professional engine builder, this is for me and me alone. As far as tools, if I don't have it, I can get it or build it.

Anyone got suggestions, or a link to a thread that will point me in the right direction as to how and where I can get the info I need?
 

E173

New Member
#3
are you allowed to use a 390 carb?
For the class I race, sure, but we run gas and they're a little harder to tune on gas. Methanol, they're a good swap. I do have a few of them to tinker with too so when all is said and done I want to be able to build them as well...I mean really they aren't that much different.
 
#4
They move a lot more air Here are some stock carbs, flow is on the float bowl. This is less than a stock head flows, the 390 stock is in the 70 CFM range. Have you tried to run one on gas and had issues?
 

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E173

New Member
#5
They move a lot more air Here are some stock carbs, flow is on the float bowl. This is less than a stock head flows, the 390 stock is in the 70 CFM range. Have you tried to run one on gas and had issues?
So yeah, they do move more air, I get that. What I'm looking for though is where to find info on building carbs, not where/what ones to try.

I have 212 and 390 carbs and multiple jets (idle and main) for both. The issue I see everywhere is that short of going to a slide carb or buying one from someone like EC, ARC, Dover, or even Paul's...who all take those same carbs and do more than change jets, there isn't info on what they're doing internally.

Jetting is easy. Putting a 390 on a 212 is easy...but I'm tired of dropping $100+ on something I know I can build myself if I can find the info on what needs to be done.

There's tons out there on building the motors, but nothing on the carb.
 
#6
When I was still able to ride and carbs were still put on bikes, the first thing I did was pull the Keihin off my Harley. I took it down to near original casting and then polished everything. These carbs today are all cast aluminum units. While the normal process will remove the large stuff, the sharp edges are still there. Polishing, (maybe some very slight grinding), will do wonders. A good rejet and the usual free flow air cleaner will really wake up most any stock carb.
 

SAS289

Well-Known Member
#7
They move a lot more air Here are some stock carbs, flow is on the float bowl. This is less than a stock head flows, the 390 stock is in the 70 CFM range. Have you tried to run one on gas and had issues?
How much more flow do you get with a stock carb bored to .675 or .690?
 
#8
No clue as I never tested one, but this is from a Johnnie Berry post and he is very honest with his posts. "Got bored during all this rain so I decided to knock out a S/A carb.. first poboy to send 100.00 to my paypal can get it...fuel circuitry hasn't been done yet so I can fix it for gas or Methanol, your choice. Flows 67cfm, .740 venturi, .820 throttle bore,big butterfly. As always I'll send it with the isolator plate and gaskets, all cut to match carburetor. "
 
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